Many silver halide photographic elements, in particular color negative films, contain so-called DIR (development inhibitor releasing) couplers. DIR couplers release inhibitors that can restrain silver development in the layer in which release occurs, as well as in other layers of a multilayer photographic material. DIR couplers can help control gamma (contrast), enhance sharpness (acutance), reduce granularity and provide color correction via interlayer interimage effects. U.S. Pat. No. 3,933,500 broadly discloses DIR couplers with azole-type coupling off groups. EP-A-0 867 763 A describes purines and 1H-pyrazolo[3,4-d]pyrimidines as DIR couplers. A specific class of DIR couplers is DI(A)R couplers (development inhibitor anchiomeric-releasing) in which the release of the inhibitor is controlled by a timing mechanism.
It is desirable that DIR couplers efficiently reduce photographic contrast to provide benefits such as enhanced sharpness, reduced granularity and improved exposure latitude. It is also desirable that they give a reduction in the total amount of developed dye density (D.sub.max).
U.S. Pat. No. 5,356,764 discloses the use of silver chloride emulsions in combination with DIRS incorporated at typically low levels with an image dye-forming coupler, e.g. the DIR comprises less than 8% of the total amount of coupler. EP 0 867 763A describes DIRs in an element containing silver chloride or silver bromoiodide at less than 11% of the total amount of coupler. JP-4278942 exemplifies silver iodide and silver bromoiodide-containing elements including DIRS at low percentage of total coupler, providing materials with good sharpness and superior shelf stability.
Silver chloride emulsions typically enable faster and easier processing, including faster and easier development, bleaching and fixing, combined with lower environmental impact.